From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH net-next-2.6] net: add rcu protection to netdev->ifalias Date: Wed, 18 May 2011 00:39:16 +0200 Message-ID: <1305671956.6741.25.camel@edumazet-laptop> References: <1303980967.3360.60.camel@edumazet-laptop> <20110428084337.6b54603e@nehalam> <20110502.152733.48516094.davem@davemloft.net> <1305670692.6741.14.camel@edumazet-laptop> <20110517152503.2f7244f3@nehalam> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: David Miller , kaber@trash.net, netdev@vger.kernel.org, remi.denis-courmont@nokia.com To: Stephen Hemminger Return-path: Received: from mail-wy0-f174.google.com ([74.125.82.174]:56868 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756695Ab1EQWjU (ORCPT ); Tue, 17 May 2011 18:39:20 -0400 Received: by wya21 with SMTP id 21so771941wya.19 for ; Tue, 17 May 2011 15:39:19 -0700 (PDT) In-Reply-To: <20110517152503.2f7244f3@nehalam> Sender: netdev-owner@vger.kernel.org List-ID: Le mardi 17 mai 2011 =C3=A0 15:25 -0700, Stephen Hemminger a =C3=A9crit= : > I am beginning to think the idea of optimizing case of "ip link show" > running in background with adding/removing network devices is silly.=20 > And switching to RCU leads to all sorts of corner cases where only > partial data will be read. Is it really worth it? >=20 Just try "modprobe dummy numdummies=3D1000", and watch load average raising, because so many processes want to hold RTNL, and the rtnl_trylock() crazy thing make them spin (restart syscall, and find RTNL locked again... wooo...) Some workloads hit RTNL quite hard, and monitoring tools were sometime frozen for unexpected long times. (before the patch, when we used to hold RTNL in dump()) I dont know, if it happens to be too hard, we'll just stick again rtnl for "ip link show" ;)